There are two types of adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT), that are also known as white fat and brown fat respectively. Consequently, these two tissues are made up of two types of fat cells.

Brown fat cells are polygonal in shape. Unlike white fat cells, these cells have considerable cytoplasm with lipid droplets scattered throughout. The nucleus is round, and, although eccentrically located, it is not in the periphery of the cell. The brown color comes from the large quantity of mitochondria. Brown fat is also known as “baby fat,” and is used to generate heat.